Hydraulic brake system for motor vehicles



May 15,1945 R. B. CAMPBELL 2,375,750

HYDRAULIC BRAKE SYSTEM FOR MOTOR VEHICLES Filed Jan. 19, 1942 54 53 55 49 50 5e @e 53 @c 5@ ce a5 75 7a 7a ticularly adaptable for use on vehicles, it is usual f hicles.

Yhicles brakes without the 'Patented May 1s, y 1945 UNITED STATES 'PATENT [orifice HYDRAULIC BRAKE SYSTEM FOR MOTOR A VEHICLES v Rodney B. campbell, North nouywqod, cam., assignor to John Eley, Jr., Los Angeles, Calif.

Appli/cation January 19, 1942, serial No. 427,252

' s claims. (ci. 5o-54.6)

This invention relates tot the iiuid brake art, and more particularly to a iiuid brake system parmotor vehicles. In standard hydraulic brake systems for motor practice to provide a supply of substantiallyv non-compressible brake fluid, such as a suitable liquid, and means for applying pressureto the brake fluid so as to feed it to the vehicle brakes. Normally, 'in such a system, the pressure is applied to the brake fluid by means of a hydraulic cylinder having a piston therein which may be actuated by mechanical or manual means, and ordinarily the pressure applied to the brake ii-uid isa function `of the pressure mechanically applied to the piston of the hydraulic cylinder. When such aiuid brake system is used on a heavy motor vehicle, such as a large truck, considerable diiiiculty isexperienced in mechanically applying sumcient force to the piston of the hydraulic cylinder to provide the vrelatively high fluid pressure required in the supply lines to operate adequately the brakes of the vehicle. This diiiiculty exists` .tiply mechanically the manual 'force applied to the brake pedals of the vehicle, as there is a limit to the effective use of such force-multiplying devices. Cnsequently, many heavy motor vel` hicles are now equipped with air brakes of the standardrailway type, in order to provide the large braking pressures required to stop such ve- There are, however, many disadvantages attendant the use of s uch standard air brakes on motor vehicles, not the least of which is the relatively high cost of installation of such a brake system.4 e

It is therefore a primary object of my invention to provide a, hydraulic brake system for vehicles in which asubstantially non-compressible brake iiuid, or liquid, is used for applying the braking force to and in which high brake fluid pressures may be instantaneously provided for actuating the venecessity oi applying large manual forces to the brake pedal of the vehicle. I accomplish this by providing a high despite manyexpedients which are used to mulhigh pressure pump and the brakes of the vehicle,

y drawing, which are for pressure uid pump .which operates at alltimes,

preferably in response to operation of the vehicle engine,- to circulate a flow4 of brake iluid at a predeterminedrhigh operating pressure through `through a suitable brake Another object of my invention is 'to provide in such a hydraulic brake system pressure accumulator means for storing uid pressure energy delivered by the high pressure pump so` that brake fluid under pressure is available in the system for actuating the brakes at al1 times, even when .the pressure pump is not operating. This is provided 'to replace the standard emergency brake on such a vehicle, so that the brakes may be set to hold the vehicle against movement when the vehicle engine and the pressure pump are not operating.

VlvStill another object'l of the invention is to provide a novel type of master brake cylinder adapted for use in such a hydraulic brake system. My master brake cylinder includes means for automatically and the iiuid pressure on the vehicle brakes when the brake valve is closed, so that iiuid pressure is applied to the brakes only when the brake valve is open. It also includes' a novel type of compensating valve which operates automatically to replace any brake fluid loss from ythe operating system through leakage orotherwise,l and includes other novel details of construction described in full hereinafter.

A further object oi' my invention is to provide. such a hydraulic brake system including safety means whereby pressure brake uid independently of the operation of the the other elements of the system, so that in the event of failure of the high pressure pump, the brake valve, the master cylinder, or any of the other units oi' the system, the vehicle brakes may still be opd erated. I prefer to accomplish this by providing a. hand pump in an auxiliary brake fluid supply line communicating Ibetween the source of brake iiuid andthe vehicle brakes. l

lOther objects and advantages of the invention will appear in the specification and in the tion only, and in which:

Fig. 1 is a diagrammatic hydraulic brake system. l

Fig. 2 is a, longitudinal sectional view of the view of my novel master brake cylinder of lmy system.y

the drawing, Fig. l shows an Referring to operating fluid reservoir ill adapted to be providedy with .a suitable supply of axsubstantially non-compressible operating iiuid, such as a liquid, and connected by piping i l with the inu take of a pressure pump I2. 1 The pressure pump i2 may be of any suitable type well known in the art adapted to deliver operating iiuid from the 'instantaneously relieving may be applied to the y the purpose of illustrarervoirl l@ under Yrelativelyhigl'i pressure. For e` ample, l prefer to utilize a pressure pump l2 which will deliver such operating uid at a pressure in the neighborhood of 1600 pounds per square inch although, obviously, either a lower or higher delivery pressure may be used without departing from the spirit of my invention.

The pressure pump l2 is arranged .to be `driven by a drive shaft I3 of the motor vehicle in which the hydraulic system is installed, and, as indicated in Fig. 1, Iv prefer to install the pump l adjacent the vehicle transmission id. Although I prefer to drive the pressure pump i2 directly from the drive shaft I3 of the motor vehicle, it d ,will be understood that any suitable source of in the scope of my invention.

The pressure pump I2 has a discharge port l@ which is connected by means of a pipe il with the inlet of a uid pressure regulator 'ld comprising a pressure regulating means of theinvention. `Thepre'ssure regulator I8 may be of any suitable type well known in the art which is adapted to deliver operating uid therethrough supplied by the pressure pump I2 at a predetermined pressure int a'pipe I9. Although the specic construction ofthe pressure regulator I8 -iorms no part of the present invention, I prefer to use such a device as Iis illustrated in my copending application, Serial No. 258,975, filed Feb-lA ru'ary 28, 1939, and issued as Pat. No. 2,310,677, to which reference is hereby made. The pressure regulator I d is also provided with an exhaust pipe 2li which connects with a iiuid return pipe 2l, one end of whichv is connected to the reservoir Ill. The pipe I9 is connected to the inlet of a check vvalve 23, the outlet of which Jis connected by a pipe connection 24 with a four-way pipe Joint 25.

The check valve 2S may bev of any suitable type adapted to permit a flow of operating uid therethrough from the pipe i3 to the pipe connection 2d, but preventing a reverse glow thereof, such as shown in my copending application, Serial No. 397,573, iledv June 1l, 194i, and issued as Pat. no. 2,306,012, to which reference is hereby 4 made.

. One side of the pipe joint 2b is connected through a pipe 26 with the valve inlet' 2li of a,A

brake valve 2t. The brake valve is is provided with a valve outlet 2Q to which is' suitably con-- nected a supply pipe Sii, and the brake valve is also provided with an exhaust port 3l which is connected by means oi an exhaust pipe d2 with the duid return pipe 2l'. The brake valve 2d is also provided with an' actuating member 3S which is so designed that when depressed it'will open the brake valve to permit a ow of operating fluid from the pipe 2li through the brake valve into the supply pipe all and when released will prevent such owopening the supply pipe il@ to communication through the brake valve with the exhaust pipe 32. Although any'suitable type of brake "valve 2t, well known in the art, may be used, Iprefer to utilize a brake valve of the type shown and described in my copending application, Serial No. 397,572, rlled June ll, lSfil, and

issued as Pat. No. 2,317,846, to which reference is hereby madefor the detalls of construction thereof which form no part of the present invention.

The supply line 30 leads to and is vconnected to a master hydraulic cylinder 3S, the details of which are shown in Fig. 2. As `shown in Fig, 2, the master hydraulic cylinder 35 includes a tubular outer shell 36 provided with external aavavco '5 di! is centrally provided with a threaded inlet port d2 into which is threaded the end of the supply pipe 3o. The head d@ is also provided with a plurali'ry ,of circumferentially 4spaced ports d3, for a purpose to be described/hereinafter, and formed l integrally with the head is an inwardlyextending cylindrical sleeve de, although, obviously, this sleeve maybe made as a separate element and suitably secured to the head d@ if desired. Supported on the vcylindrical sleeve dil is an axially l 1.1 movable piston sleeve d5 having an annular shoulpower for actuating the pump may be used withder it `formed thereon and provided with an annular flange dll against which abuts an annular packing du, preferablyof the chevron type, which .is held in position by a suitable nut is threaded 11 on the piston sleeve d5 and locked against movement by a lock nut 5d having an annular V-groove 52 fornledv in the end face thereof; Mounted .on the annular flange 4l is a tubular extension 53, which is oil greater diameter than the diameter z5- of the pistonsleeve 35, the outer end of which is'mternally threaded to receive a packing follower ring 5d which serves to clamp an annular packing 55, also preferably on the chevron type,

against the iiange 4l. As will be evident, the an- -rm nuiar packing d8 forms a\il"uid seal between the piston sleeve l and the internal wall of the tubularl outer shell 3d, and the annular packing 55 forms a iiuid seal between' the piston sleeve d5 and the external wall of the cylindrical sleeve Ml.'

K5 The piston sleeve d5, together with the other parts mounted thereon, forms a fluid piston means of the invention.

The rightward end, of the piston sleeve 45, as

seen in Fig. 2', is iiternally threaded to receive 4" a sleeve head 5d, the vinner face of which is provided with an annular packing 5l, preferably of the chevron type, which is held in place by a y suitable snap ringd and serves to form a iiuidtrai chamber d@ is an annular valve seat member d2 which engages a washer @3 and is clamped in place by a follower element dit which is threaded into the central chamber. The ol lower element @d is locked in place by an exm remedy threaded annular lock auf. se which is also threaded into the central chamber 59;. Supported on the annular valve seat member 52,

and normally closing the same, is a ball valve member d@ which is at all times resilientlyurged m toward seating relation/'with the valve seat member by a helical compression spring 6l, The sleeve head 5@ and the parts mounted therein constitute a compensating valve means de oi the invention, and, as is evident, normally close the myfyrightward end of the piston sleeve d5.

The rightward end of the tubular outer shell d@ is closed bya second head d which is clamped against 'the rightward end of the outer shell by alsecond annular clamping sleeve ld which is 7@ suitably threaded to the oui-.er sneu and locked relative thereto by a suitable lock nut ll. An annular, inwardly extending ring l2 is formed on the `inner face of the second head t9, and disposed between this ring and the outer shell w is an annular packing element l2, preferably of s' tight joint between the sleeve head 5t and the let port, 'll adapted to in the art which is that so long as fluid at a the chevron type, vwhich insures an eiectlve seal between the second head 69 and the outer shell 35. Formed at the center of the second head 58 is an inwardly extending boss 'I4 in which is secured an inwardly extending pin member 'I5 i which, it will be observed, is'axially aligned with the annular valve seat member 62 and which serves as an actuating' means to unseat the ball valve member (it as described hereinafter. En-

i gaging the annular packing element 'I8 is a main compression spring 18, the other end of which engages inthe V-gr'oove 52 of the nut 49 carried on the piston sleeve 45, and which is under apredetermined compression tending to normally move the piston sleeve 45 toward the inlet portv 42 and away from the second' head 59. Also formed in the second head 58 is a threaded outreceive a pipe connection 'i9 of a fluid distribution system 8U which leads to the vehicle brakes (not shown) as is Well known in the art. A separate fluid line 8l may also obe providedif desired as a fluid takeoif leading to a trailer or other device to be operated by the Viluid in the distribution system, if desired.

Connected` to the pipe 26 through the four-l way pipe joint 25 and an accumulator p'ipe 82 is a uid pressure accumulator device 83, which may be of any type well known in the art, and which 4=is adapted to store fluid under-pressure and automatically deliver the same through the accumulator pipe 82 to the pipe 26 upon a predetermined reduction in fluid pressure in the pipe 26. v

I also prefer to incorporate with my hydraulic brake system anl auxiliary pumping means whereby operating uid may be pumped from the reservoir III to the fluid distribution sysand the equipment connected thereto, so thatin thel event of failure of any of the principal equipment, asin an emergency; the brakes of the vehicle may still be actuated by an indevvalve 89 to an auxiliary pressure supply pipe 90 which communicates directly with the fluid distribution system 80. 'The emergency cut-over valve 89 is'also connected by a pipe 9i to the four-way pipe joint 25 so that operating fluid under pressure may to the emergency cut-over valve from the pump I2 while the pump is operating. The emergency cut-over valve 89 maybe of any type well known so constructed and arranged sure is maintainedin the pipe 9i the cut-over valve is closed to prevent operation of the hand pump 85, but which will automatically permit communication between the discharge pipe 88 and the auxiliary vpressure supply pipe 9'! through the cut-over valve whenever the fluid pressure in the pipe 8l drops below a predetermined minimum. I prefer to use an emergency cut-over valve of the type shoWnand-describecl in my copending application, Serial No. 412 117, filed September 24, 1941,A and issued as Pat. No. 2,312,686, although any suitable type oi' such device may be used as desired. Furthermore, ifl

be supplied therethroughV predetermined pres- Upon operation of the ,ably in the neighborhood of tem 8U independently of the pressure pump I2 25 through the pipe fluid therethrough from the desired, .the emergency cut-over valve 88 and the may be omitted from the system and the pipe 9i pipe connection 88 connected directly to the auxiliary pressure supply pipe 90 so that at any time the hand pump may be actuated to inde` pendently supply operating fluid from the reservoir I Il to the -distribution system 80. However, it will generally be -found desirable to incorporate some form of emergency cut-over valve, such as the cut-over valve 89, to prevent actuation of the hand pump 85 except when such actuation is required by a failure in the parallel supply system. A

In operation, as indicated. the 'fluid distribution system 88 is suitably connected to one or more hydraulic brakes on the motor vehicle, as

desired and as well known in the art, and is preferably separately filled with operating fluid. engine of the vehicle, the drive shaft I3 rotates to operate the pressure pump I2, which draws operating uid from the reservoir Ill through the piping II and discharges it at relatively high pressure, prefer- 1000 pounds per square inch or more, into the pipe Il through which it is conveyed into the iiuid pressure regulater I8. The fluid pressure regulator I8 is adapted to discharge operating fluid from the pipe I'I into the.pipe I 9 to maintain operating.

fluid in the pipe I9 at a predetermined pressure, which may be at or below the pressure of the operating iiuid in the pipe I'I. The balance of the operating fluid conveyed through the pipe I 'l is exhausted through the pressure regulator I8 into the exhaust pipe 28 and is conveyed through the fluid return pipe 2l back to the relservoir I8. It will thus be observed that during .operation of the pressure pump I2, iluidl cir- `cuiates from the "reservoir Ill therethroughand through the pressure regulator I8 and back to the reservoir, providing a constant circulation of fluid in this cycle so long as the pressure pump l |2is operating.u

Operating fluid is conveyed from the pressure regulator I8 through the pipe I9 and the check valve 23 and the pipe connection 24 to the four; way pipe joint 25. It iiows. from the pipe joint 8l to the emergency cut-over valve 89, to 4close the same to prevent actuation of the hand pump 85. It also flows through the accumulator pipe 82 to the iiuid pressure accumulator device 83 to build up the desired line pres-` sure therein and store the same. It also flows vthrough the pipe 26 to the valve inlet 21 of the brake valve 28.- So long as the actuating member 33 of the brake valve 28 is not depressed, the brake valve remains closedto prevent a now of operating uid from the pipe 25 into the supply pipe 30 through the brake valve. A the actuating member 33 is depressed, the `brake valve 28 is opened to permit a iiow of operating pipe 26 into the supply .pipe 30 through which it flows to the inlet port 42 of the master hydraulic cylinder 35.

Operating fluid iiows into cylinder 35 through the inlet port 42 and to the interior of the cylindrical sleeve 44 to exert the relatively highsupply line pressure on the sleeve head 56of th piston sleeve 45, which tends to move the piston sleeve away from the rst head 40 and toward the second head tgagainst` the f However, when the master hydraulic i Movement of the piston sleeve t5 to the right, Y

as seen in Fig. 2. displaces operating `fluid from the right-hand end of the outer shell 36 through the outlet port ll into the distribution system 80 to operate the wheel brakes of the vehicle, as is well known in the art. The actual minimum fluid displacement of the outer shell 36 required is governed by the minimum volume oi. operating fluid needed to fully actuate the wheel brakes, and in practice I prefer to design my device so that the total possible displacement of operating fluid from the outer shell 36 is slightly greater than the displacement actually required to fully actuate the wheel brakes, for example, two or three cubic inches greater. This provision is made in design in order to provide for minor volumetric losses of operating fluid in the distribution system arising from iluctuations in the temperature of the operating uid or slight leakage. Major volumetric loss in the operating fluid in the distribution system 8B is corrected by the compensating valve means t8, as described, hereinafter.

It is to be noted that the master hydraulic cylinder 35 is in effect divided into a small volume, high pressure chamber 92 formed by the cylindrical sleeve lili, which at all times is in open communication with the inlet port d2, anda large volume, low pressure chamber 93 formed by the rightward end of the outeru shell 3S, which at all times is in 'open communication with the outlet port il. Preferably, the volume of the low pressure chamber si) is approximately three times that of the high pressure chamber 02, so as to provide a pressure differential of about three to one therebetween; Thus, the maximum fluid pressure developed in the low pressure chamber 93, upon movement of the piston sleeve te to the right, is only about one-third of that applied.V to the high pressure chamber s2, with the highly desirable result that a smooth wheel brake applicaf-l asvavso operating fluid.v In such event, u rlghtward movement of the piston sleeve, instead ci' stopping its rightward travel before engagement with the pin member l5 as during normal opera.-

tion, it continues to move to the right until the to reseat on the annular valve seat member 62 V under the action of the helical compression spring all. Due to the pressure-area dierential between the high pressure chamber Q2 and the low pressure chamber t3, the fluid pressure applied to the Wheel brakes through the distribution system 80 While the compensating valve means B8 is open cannot exceed the maximum iluid pressure normally developed in the low pressure chamber 93 during the normal rightward stroke of the piston sleeved, thus preventing abnormal and possibly dangerous fluid pressures from being applied to the wheel brake mechanisms. It will thus be appreciated that the compensatingvalve means 68 operates automatically when required to replenish any undesirable depletion of the volume of operating uid in the fluid distribution system-S0 to maintain at all times sulcient operating fluid in the distribution system to fully actuate the wheel brakes.

It is also to be notedV that in the event that the volume of operating fluid in the distribution system 80 tends to expand, due to an increase in temperature thereof or from other causesthe ball valve member S6 of the compensating valve means t8 is unseated by such expansion to permit any excess operating uid from the distribution tion can be obtained oven though a high operating pressure, for example in the neighborhood of 1000 pounds per square inch, is used to actuate the master hydraulic cylinder 35.

- the wheel brakes'of the vehicle, and thus prevents v Due to the fact that the fluid displacement volume of the low pressure chamber @il is greater than the normal displacement volume of oper-A ating fluid in the distribution system 30 required to apply fully the wheel brakes of the vehicle, as pointed out above, upon admission of operating fluid to the high pressure chamber t2 the piston sleeve t5 normally moves to the right and completes its rightward stroke by stopping short oi4 engagement with the pin member 15, having thus fully applied the vehicle brakes. Upon release of the actuating member 33 of the brake valve 28,

.the supply line 30 is again automatically connected tothe exhaust pipe 32, which is` at relatively low reservoir or exhaust pressure, as described above, and the piston sleeve immediately returns to the position shown in Fig. 2, under the action of the fluid pressure in the distribution system 80 and the force exerted by the main compression spring 16. s

In thel event that the volumeA of operating fluid in the distribution system 80- is materially reduced, as a. result of fluid leakage or otherwise, the compensating valve means 68 automatically operates to replenish the distribution system with lowing claimssystem to return to the reservoir l@ through the brake valve 2t and the exhaust pipe 32.. This effectively prevents undesired rises in pressure of the operating fluid in the distribution system 80, which would otherwise tend to apply partially unnecessary wear on the brake mechanisms.

In the event of failure of the pressure Vpump I 2, the fluid pressure regulator l 8, the brake valve '28, the master hydraulic cylinder 35, or any of rthe pipe connections therebetween, as in an emergency, operating nuid may still be manually pumped from the reservoir l0 to the uid distribution systemV 80 by the hand pump 85 to actuate the wheel brakes. This is a desirable safety feature of the invention.

Although I have shown and described a preferred embodiment of my invention, it will be appreciated that certain' units, parts, and mechanisms may-be substituted for those `disclosed herein, without departing from the spirit of my invention, and, cons equently,-I do not intend to be limitedby the specic terms of my disclosure but desire to be' afforded the I claim as my invention: 1. In a master cylinder device,

a' stationary sleeve iilidly mounted in said outer fullscope of the folthefcombination of: atubular outer shell; a rst head clos- I shell relative to said rst head, said inlet port communicating with the interior of said sleeve; an axially movable sleeve carried on said stationary sleeve; piston means secured on one end of said movable sleeve adjacent said inlet port and forming a fluid seal with the interior of said outer shell; a separate sleeve head threaded to and closing the other end of said movable sleeve;`

valve means carried by said sleeve head; actuating means for opening said valve means in response to axial movement of said movable sleeve, said actuating means being mounted on said second head; and spring means in said outer shell surroundingA said movable sleeve and engaging said piston so as to normally urge it toward said first head.

2. In a master cylinder device, the combination of a tubular'outer shell; a ilrst head closing one end of said outer shell and having an inlet port therein; a second head closing the other end of. said outer shell,-there being an outlet port communicating with said other end of said shell; a stationary sleeve rigidly mounted on said iirst head and concentric with said outer shell, said inlet .port communicating with the interior of said stationary sleeve; an axially movable sleeve carried on said stationary sleeve; annular piston means secured to said movable sleeve at its end toward said inlet port and forming a uid seal with the interior of said outer shell; a sleeve head closing the nother end of said movable sleeve; a spring-held` check valve carried by said sleeve head and adapted to open toward said inlet port; a pin on said second head extending into said outer shell in alignment with said check'valve and adapted to open said check valve in response to a predetermined axial movement of said sleeve head toward said second head; and spring means in said outer shell surrounding said movable sleeve and engaging said piston so as to normally urge it toward said rst head.

3. In a master cylinder device, the combination of: a tubular outer shell; a rst head closing one end of said outer shell and having an irllet port therein; a second head closing the other end of said outer shell, there being an outlet port communicating with said other end of said shell;

a stationary sleeve mounted on said rst head l ing a fluid seal between said movable sleeve and said outer shell, said flange and said outer sealing means forming a piston; an inner annular sealing means within said movable sleeve adjacent said outer sealing means and forming a fluid seal between said movable sleeve and said stationary sleeve; a sleeve head closing the end of said movable sleeve adjacent said outlet port; check valve means carried by said sleeve head adapted to open toward said inlet to permit a ilow of fluid from said inlet to said outlet but preventing a reverse ow; actuating means carried by said second head and adapted to open said check valve means upon a predetermined travel of said Asleeve head toward said second head; and spring means in said outer shell en gaging said second head and telescoped over said movable sleeve to engage said piston and extending substantially the length of said outer shell when said movable sleeve is in a retracted position closest to said first head.

RODNEY B. CAMPBELL. 

